Lubricating oil compositions with oxidative stability in diesel engines

ABSTRACT

A method for improving oxidative stability of a lubricating oil in a diesel engine by using as the lubricating oil a formulated oil. The formulated oil has a composition including a lubricating oil base stock as a major component, and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock as minor components. The at least one aminic antioxidant is present in an amount from 0.1 to 2.5 wt. %, the at least one phenolic antioxidant is present in an amount from 0.5 to 5 wt. %, and the at least one Group V base stock is present in amount from 1 to 20 wt. %. Oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than specified antioxidants and Group V base stock.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/589,722, filed on Nov. 22, 2017, the entire contents of which are incorporated herein by reference.

FIELD

This disclosure relates to lubricating oils with oxidative stability in diesel engines. In particular, this disclosure relates to lubricating oils for diesel engines, and methods for improving oxidative stability of a lubricating oil in a diesel engine lubricated with the lubricating oil. The lubricating oils of this disclosure are useful as passenger vehicle engine oil (PVEO) products or commercial vehicle engine oil (CVEO) products.

BACKGROUND

Lubricating oils are an essential part of modern vehicle design for engine operation and protection. One essential feature of engine oil is the viscosity, which must be viscous enough to lubricate effectively without being so viscous that the engine cannot effectively distribute the fluid to parts of the engine that need lubrication. Viscosity is also closely linked to fuel economy, with higher viscosity detracting from fuel efficiency. Oxidation of molecules in lubricating oils can cause oligomerization and eventually result in a dramatic, irreversible increase in the viscosity of the oil. Such increase in oil viscosity can both hamper the operation of the engine and reduce efficiency. Antioxidant molecules are typically added to lubricating oils to protect the composition from such oxidative degradation and control viscosity increase during engine operation.

In the U.S., CAFE and GHG, emission regulations demand a dramatic increase in fuel efficiency over the next few decades. These regulations are driving automakers to downsize engines while maintaining or even increasing engine power. As a result, engines run at hotter temperatures on average and subject engine oils to increasingly harsh oxidative conditions during engine operation. This trend has accelerated the demand for improved oxidative stability in engine oils and has triggered the development of the Volvo T-13 Engine Oil Oxidation Test (ASTM D8048), for the API heavy duty diesel engine oil categories CK-4 and FA-4.

Antioxidant additives are included in engine oil formulations to protect the oil against oxidative degradation. Commonly used antioxidant molecules include alkylated diarylamines and 2,4,6-trisubstituted phenols. Over the past several decades, the aminic and phenolic antioxidants have been shown to function synergistically when added in combination to finished engine oil compositions, protecting engine oil and hardware from oxidation across a range of different temperatures. Total antioxidant content for heavy duty engine oils has typically been approximately 1.5% to meet expectations for oxidative stability in engine test and field performance.

Improved oxidation stability is necessary to increase oil life in diesel engines and oil drain intervals, thus reducing the amount of used oil generated as a consequence of more frequent oil changes. Longer oil life and oil drain intervals are key benefits that are desirable to end customers. Traditional antioxidant packages provide standard protection leaving the main differentiation hinging on the quality of the base stock in the formulation.

What is needed is newly designed lubricants for diesel engines capable of controlling oxidation and oil thickening for longer periods of time as compared to conventional lubricants. Further, what is needed is newly designed lubricants for diesel engines that enable extended oil life in combination with desired oxidative stability.

SUMMARY

This disclosure relates to lubricating oils with oxidative stability in diesel engines. In particular, this disclosure relates to lubricating oils for diesel engines, and methods for improving oxidative stability of a lubricating oil in a diesel engine lubricated with the lubricating oil. The lubricating oils of this disclosure are useful as passenger vehicle engine oil (PVEO) products or commercial vehicle engine oil (CVEO) products.

This disclosure also relates in part to a method for improving oxidative stability of a lubricating oil in a diesel engine by using as the lubricating oil a formulated oil. The formulated oil has a composition comprising a lubricating oil base stock as a major component, and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components. The lubricating oil base stock is present in an amount from about 1 to about 95 weight percent, based on the total weight of the lubricating oil. The at least one aminic antioxidant is present in an amount from about 0.1 to about 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from about 0.5 to about 5 weight percent, and the at least one Group V base stock is present in an amount from about 1 to about 20 weight percent, all based on the total weight of the lubricating oil. Oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048.

This disclosure further relates in part to a lubricating oil having a composition comprising a lubricating oil base stock as a major component, and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components. The lubricating oil base stock is present in an amount from about 1 to about 95 weight percent, based on the total weight of the lubricating oil. The at least one aminic antioxidant is present in an amount from about 0.1 to about 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from about 0.5 to about 5 weight percent, and the at least one Group V base stock is present in an amount from about 1 to about 20 weight percent, all based on the total weight of the lubricating oil. Oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048.

It has been surprisingly found that, for lubricating oils of this disclosure containing a minor component having at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048.

In particular, it has been surprisingly found that, for lubricating oils of this disclosure containing a minor component having at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the number of hours to break as measured by Fourier-transform infrared spectroscopy (FT-IR) or by kinematic viscosity at 40° C. (KV40) of the lubricating oil, is increased as compared to the number of hours to break as measured by FT-IR or KV40 of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.

Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the composition of lubricating oil formulations and testing results in accordance with the Examples.

FIG. 2 shows the performance of formulations described in FIG. 1 in the Volvo T-13 engine test in accordance with the Examples.

FIG. 3 shows the composition of lubricating oil formulations, and testing results including the results of Sequence IIIH oxidation tests, in accordance with the Examples.

FIG. 4 shows the composition of lubricating oil formulations, and testing results including the results of Mack T-12 engine tests, in accordance with the Examples.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. The phrase “major amount” as it relates to components included within the lubricating oils of the specification and the claims means greater than or equal to 50 wt. %, or greater than or equal to 60 wt. %, or greater than or equal to 70 wt. %, or greater than or equal to 80 wt. %, or greater than or equal to 90 wt. % based on the total weight of the lubricating oil. The phrase “minor amount” as it relates to components included within the lubricating oils of the specification and the claims means less than 50 wt. %, or less than or equal to 40 wt. %, or less than or equal to 30 wt. %, or greater than or equal to 20 wt. %, or less than or equal to 10 wt. %, or less than or equal to 5 wt. %, or less than or equal to 2 wt. %, or less than or equal to 1 wt. %, based on the total weight of the lubricating oil. The phrase “essentially free” as it relates to components included within the lubricating oils of the specification and the claims means that the particular component is at 0 weight % within the lubricating oil, or alternatively is at impurity type levels within the lubricating oil (less than 100 ppm, or less than 20 ppm, or less than 10 ppm, or less than 1 ppm). The phrase “other lubricating oil additives” as used in the specification and the claims means other lubricating oil additives that are not specifically recited in the particular section of the specification or the claims. For example, other lubricating oil additives may include, but are not limited to, antioxidants, detergents, dispersants, antiwear additives, corrosion inhibitors, viscosity modifiers, metal passivators, pour point depressants, seal compatibility agents, antifoam agents, extreme pressure agents, friction modifiers and combinations thereof.

This disclosure relates to lubricating oils for diesel engines containing a combination of aminic and phenolic antioxidants at high concentration of phenolic antioxidant (e.g., greater than about 0.7, 1.0, 1.5, 2.0, 2.5, 3.0, 3.3 weight percent or greater) with a more typical level of aminic antioxidant (e.g., about 0.7 weight percent). Lubricating oils formulated with this level and combination of antioxidants provide unexpectedly good oxidative stability as measured by the Volvo T-13 Engine Oil Oxidation Test (ASTM D8048). Other engine tests for oxidation performance, such as the Sequence IIIH (ASTM D8111) and the Mack T-12 (ASTM D7422) do not show a corresponding benefit from increased phenolic antioxidant content. Bench oxidation tests, such as high pressure differential scanning calorimetry (HPDSC), also show no benefit from increased phenolic antioxidant content. Furthermore, when lubricating oils contain a high concentration of phenolic antioxidant and a moderate amount of Group V base stock, the oxidation performance in the Volvo T-13 is, surprisingly, further improved as compared to a lubricating oil composition containing only a high level of hindered phenolic antioxidant.

In accordance with this disclosure, when a combination of aminic and phenolic antioxidants at high concentration of phenolic antioxidant and a moderate amount of Group V base stock is used in the lubricating oil formulation, excellent oxidation control is observed along with improvement in viscosity control and deposit control as measured by the Volvo T-13 Engine Oil Oxidation Test (ASTM D8048).

In particular, for lubricating oils of this disclosure containing a minor component having at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the number of hours to break as measured by Fourier-transform infrared spectroscopy (FT-IR) or by kinematic viscosity at 40° C. (KV40) of the lubricating oil, is increased as compared to the number of hours to break as measured by FT-IR or KV40 of a lubricating oil containing a minor component other than the at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock.

In accordance with this disclosure, a method is provided to improve oxidative stability through the lifetime of a lubricant in diesel engines through selection of a combination of aminic and phenolic antioxidants, at high concentration of phenolic antioxidant, and a moderate amount of Group V base stock, in combination with Group I, Group II, Group III, Group IV or Group V base stocks. Specifically, when from 1-20 weight percent of a Group V base stock is used in the formulation containing the at least one aminic and at least one phenolic antioxidant, the lubricant oxidation performance is significantly improved as compared to formulations not containing a hindered phenolic antioxidant and/or a Group V base stock.

Further, in accordance with this disclosure, finished lubricants can be designed that are capable of controlling oxidation and oil thickening for long durations in diesel engines as compared to lubricants not having a combination of aminic and phenolic antioxidants, at high concentration of phenolic antioxidant, and a moderate amount of Group V base stock. This disclosure also enables extended oil life in combination with superior viscosity control, deposit control and cleanliness performance through a balance of antioxidant chemistry.

Employing a combination of aminic and phenolic antioxidants, at high concentration of phenolic antioxidant, and a moderate amount of Group V base stock, allows for an improvement in oxidative stability, highlighting potential synergies with lower concentrations of aminic antioxidants.

Lubricating Oil Base Stocks

A wide range of lubricating base oils is known in the art. Lubricating base oils that are useful in the present disclosure are both natural oils, and synthetic oils, and unconventional oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad base oil stock categories developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between about 80 to 120 and contain greater than about 0.03% sulfur and/or less than about 90% saturates. Group II base stocks have a viscosity index of between about 80 to 120, and contain less than or equal to about 0.03% sulfur and greater than or equal to about 90% saturates. Group III stocks have a viscosity index greater than about 120 and contain less than or equal to about 0.03% sulfur and greater than about 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90 and/or >0.03% and ≥80 and <120 Group II ≥90 and ≤0.03% and ≥80 and <120 Group III ≥90 and ≤0.03% and ≥120 Group IV Polyalphaolefins (PAO) Group V All other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification, for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks, including synthetic oils such as polyalphaolefins, alkyl aromatics and synthetic esters are also well known base stock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oils such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks are commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are known materials and generally available on a major commercial scale from suppliers such as ExxonMobil Chemical Company, Chevron Phillips Chemical Company, BP, and others, typically vary from about 250 to about 3,000, although PAO's may be made in viscosities up to about 150 cSt (100° C.). The PAOs are typically comprised of relatively low molecular weight hydrogenated polymers or oligomers of alphaolefins which include, but are not limited to, C₂ to about C₃₂ alphaolefins with the C₈ to about C₁₆ alphaolefins, such as 1-hexene, 1-octene, 1-decene, 1-dodecene and the like, being preferred. The preferred polyalphaolefins are poly-1-hexene, poly-1-octene, poly-1-decene and poly-1-dodecene and mixtures thereof and mixed olefin-derived polyolefins. However, the dimers of higher olefins in the range of C₁₄ to C₁₈ may be used to provide low viscosity base stocks of acceptably low volatility. Depending on the viscosity grade and the starting oligomer, the PAOs may be predominantly trimers and tetramers of the starting olefins, with minor amounts of the higher oligomers, having a viscosity range of 1.5 to 12 cSt. PAO fluids of particular use may include 3.0 cSt, 3.4 cSt, and/or 3.6 cSt and combinations thereof. Bi-modal mixtures of PAO fluids having a viscosity range of 1.5 to 150 cSt may be used if desired.

The PAO fluids may be conveniently made by the polymerization of an alphaolefin in the presence of a polymerization catalyst such as the Friedel-Crafts catalysts including, for example, aluminum trichloride, boron trifluoride or complexes of boron trifluoride with water, alcohols such as ethanol, propanol or butanol, carboxylic acids or esters such as ethyl acetate or ethyl propionate. For example the methods disclosed by U.S. Pat. No. 4,149,178 or 3,382,291 may be conveniently used herein. Other descriptions of PAO synthesis are found in the following U.S. Pat. Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156; 4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ to C₁₈ olefins are described in U.S. Pat. No. 4,218,330.

The alkylated naphthalene can be used as base oil or base oil component and can be any hydrocarbyl molecule that contains at least about 5% of its weight derived from a naphthenoid moiety, or its derivatives. These alkylated naphthalenes include alkyl naphthalenes, alkyl naphthols, and the like. The naphthenoid group can be mono-alkylated, dialkylated, polyalkylated, and the like. The naphthenoid group can be mono- or poly-functionalized. The naphthenoid group can also be derived from natural (petroleum) sources, provided at least about 5% of the molecule is comprised of the naphthenoid moiety. Viscosities at 100° C. of approximately 3 cSt to about 50 cSt are preferred, with viscosities of approximately 3.4 cSt to about 20 cSt often being more preferred for the naphthalene component. In one embodiment, an alkyl naphthalene where the alkyl group is primarily comprised of 1-hexadecene is used. Other alkylates of naphthalene can be advantageously used. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like.

Alkylated naphthalenes of the present disclosure may be produced by well-known Friedel-Crafts alkylation of aromatic compounds. See Friedel-Crafts and Related Reactions, Olah, G. A. (ed.), Inter-science Publishers, New York, 1963. For example, an aromatic compound, such as naphthalene, is alkylated by an olefin, alkyl halide or alcohol in the presence of a Friedel-Crafts catalyst. See Friedel-Crafts and Related Reactions, Vol. 2, part 1, chapters 14, 17, and 18, See Olah, G. A. (ed.), Inter-science Publishers, New York, 1964. Many homogeneous or heterogeneous, solid catalysts are known to one skilled in the art. The choice of catalyst depends on the reactivity of the starting materials and product quality requirements. For example, strong acids such as AlCl₃, BF₃, or HF may be used. In some cases, milder catalysts such as FeCl₃ or SnCl₄ are preferred. Newer alkylation technology uses zeolites or solid super acids.

Mixtures of alkylated naphthalene base stocks with other lubricating oil base stocks (e.g., Groups I, II, III, IV and V base stocks) may be useful in the lubricating oil formulations of this disclosure.

The alkylated naphthalene can be present in an amount of from about 1 to about 99.8 weight percent, or from about 1 to about 95 weight percent, or from about 1 to about 90 weight percent, or from about 1 to about 85 weight percent, or from about 5 to about 80 weight percent, or from about 1 to about 75 weight percent, or from about 1 to about 70 weight percent, based on the total weight of the formulated oil. Preferred concentrations of alkylated naphthalene may also be in the range from about 1 weight percent to about 20 weight percent in some embodiments of the disclosure, or preferably from about 2 weight percent to about 18 weight percent, or more preferably from about 3 weight percent to about 16 weight percent, or even more preferably from about 4 weight percent to about 12 weight percent, or perhaps even more preferably from about 5 weight percent to about 10 weight percent.

Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of mono-carboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols (such as the neopentyl polyols, e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol) with alkanoic acids containing at least about 4 carbon atoms, preferably C₅ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Suitable synthetic ester components include the esters of trimethylol propane, trimethylol butane, trimethylol ethane, pentaerythritol and/or dipentaerythritol with one or more monocarboxylic acids containing from about 5 to about 10 or more carbon atoms. These esters are widely available commercially, for example, the Mobil P-41 and P-51 esters of ExxonMobil Chemical Company.

Preferred synthetic esters useful in this disclosure have a kinematic viscosity at 100° C. of about 3 cSt to about 50 cSt, preferably about 3 cSt to about 30 cSt, more preferably about 3.5 cSt to about 25 cSt, and even more preferably about 2 cSt to about 8 cSt. Group V base oils useful in this disclosure preferably comprise an ester at a concentration of about 2% to about 20%, preferably from about 5% to about 15%.

Also useful are esters derived from renewable material such as coconut, palm, rapeseed, soy, sunflower and the like. These esters may be monoesters, di-esters, polyol esters, complex esters, or mixtures thereof. These esters are widely available commercially, for example, the Mobil P-51 ester of ExxonMobil Chemical Company.

Engine oil formulations containing renewable esters are included in this disclosure. For such formulations, the renewable content of the ester is typically greater than about 70 weight percent, preferably more than about 80 weight percent and most preferably more than about 90 weight percent.

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Other useful lubricant oil base stocks include wax isomerate base stocks and base oils, comprising hydroisomerized waxy stocks (e.g. waxy stocks such as gas oils, slack waxes, fuels hydrocracker bottoms, etc.), hydroisomerized Fischer-Tropsch waxes, Gas-to-Liquids (GTL) base stocks and base oils, and other wax isomerate hydroisomerized base stocks and base oils, or mixtures thereof Fischer-Tropsch waxes, the high boiling point residues of Fischer-Tropsch synthesis, are highly paraffinic hydrocarbons with very low sulfur content. The hydroprocessing used for the production of such base stocks may use an amorphous hydrocracking/hydroisomerization catalyst, such as one of the specialized lube hydrocracking (LHDC) catalysts or a crystalline hydrocracking/hydroisomerization catalyst, preferably a zeolitic catalyst. For example, one useful catalyst is ZSM-48 as described in U.S. Pat. No. 5,075,269, the disclosure of which is incorporated herein by reference in its entirety. Processes for making hydrocracked/hydroisomerized distillates and hydrocracked/hydroisomerized waxes are described, for example, in U.S. Pat. Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as well as in British Patent Nos. 1,429,494; 1,350,257; 1,440,230 and 1,390,359. Each of the aforementioned patents is incorporated herein in their entirety. Particularly favorable processes are described in European Patent Application Nos. 464546 and 464547, also incorporated herein by reference. Processes using Fischer-Tropsch wax feeds are described in U.S. Pat. Nos. 4,594,172 and 4,943,672, the disclosures of which are incorporated herein by reference in their entirety.

Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized (wax isomerate) base oils be advantageously used in the instant disclosure, and may have useful kinematic viscosities at 100° C. of about 3 cSt to about 50 cSt, preferably about 3 cSt to about 30 cSt, more preferably about 3.5 cSt to about 25 cSt, as exemplified by GTL 4 with kinematic viscosity of about 4.0 cSt at 100° C. and a viscosity index of about 141. These Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized base oils may have useful pour points of about −20° C. or lower, and under some conditions may have advantageous pour points of about −25° C. or lower, with useful pour points of about −30° C. to about −40° C. or lower. Useful compositions of Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and wax-derived hydroisomerized base oils are recited in U.S. Pat. Nos. 6,080,301; 6,090,989, and 6,165,949 for example, and are incorporated herein in their entirety by reference.

The hydrocarbyl aromatics can be used as base oil or base oil component and can be any hydrocarbyl molecule that contains at least about 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and the like. The aromatic can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from about C₆ up to about C₆₀ with a range of about C₈ to about C₂₀ often being preferred. A mixture of hydrocarbyl groups is often preferred, and up to about three such substituents may be present. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least about 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 3 cSt to about 50 cSt are preferred, with viscosities of approximately 3.4 cSt to about 20 cSt often being more preferred for the hydrocarbyl aromatic component. In one embodiment, an alkyl naphthalene where the alkyl group is primarily comprised of 1-hexadecene is used. Other alkylates of aromatics can be advantageously used. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be about 2% to about 25%, preferably about 4% to about 20%, and more preferably about 4% to about 15%, depending on the application.

Alkylated aromatics such as the hydrocarbyl aromatics of the present disclosure may be produced by well-known Friedel-Crafts alkylation of aromatic compounds. See Friedel-Crafts and Related Reactions, Olah, G. A. (ed.), Inter-science Publishers, New York, 1963. For example, an aromatic compound, such as benzene or naphthalene, is alkylated by an olefin, alkyl halide or alcohol in the presence of a Friedel-Crafts catalyst. See Friedel-Crafts and Related Reactions, Vol. 2, part 1, chapters 14, 17, and 18, See Olah, G. A. (ed.), Inter-science Publishers, New York, 1964. Many homogeneous or heterogeneous, solid catalysts are known to one skilled in the art. The choice of catalyst depends on the reactivity of the starting materials and product quality requirements. For example, strong acids such as AlCl₃, BF₃, or HF may be used. In some cases, milder catalysts such as FeCl₃ or SnCl₄ are preferred. Newer alkylation technology uses zeolites or solid super acids.

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Non-conventional or unconventional base stocks/base oils include one or more of a mixture of base stock(s) derived from one or more Gas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate base stock(s) derived from natural wax or waxy feeds, mineral and or non-mineral oil waxy feed stocks such as slack waxes, natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks.

GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from about 2 mm²/s to about 50 mm²/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to about −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of about 80 to about 140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than about 10 ppm, and more typically less than about 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this materially especially suitable for the formulation of low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).

Base oils for use in the formulated lubricating oils useful in the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features.

This other base oil typically is present in an amount ranging from about 0.1 to about 90 weight percent, or from about 1 to about 80 weight percent, or from about 1 to about 70 weight percent, or from about 1 to about 60 weight percent, or from about 1 to about 50 weight percent, based on the total weight of the composition. The base oil may be selected from any of the synthetic or natural oils typically used as crankcase lubricating oils for spark ignition and compression-ignited engines. The base oil conveniently has a kinematic viscosity, according to ASTM standards, of about 2.5 cSt to about 12 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 9 cSt (or mm²/s) at 100° C. Mixtures of synthetic and natural base oils may be used if desired. Mixtures of Group II, III, IV, and V may be preferable.

Aminic and Phenolic Antioxidants

The formulated lubricating oil of the present disclosure contains a combination one or more aminic antioxidants and one or more phenolic antioxidants. Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197, for example.

The lubricant compositions of this disclosure include a minimum level of a specific combination of antioxidant components. The specific antioxidant combination includes: (i) a high concentration of phenolic antioxidant, and (ii) a more typical concentration of an aminic antioxidant. The phenolic antioxidant component is present in the lubricating compositions at a minimum of 0.5, 0.6, 0.7, 1.0, 1.3, 2.0, 3.0 or a minimum 3.3 percent by weight or higher. The aminic antioxidant component is present in an amount of less than 2.5, 2.0, 1.5, 1.0, 0.8 or 0.75 weight percent. In the lubricating compositions of this disclosure, the concentration of phenolic antioxidant is greater than the concentration of aminic antioxidant. The ratio of the weight percent of the hindered phenolic antioxidant to the aminic antioxidant (based on the total weight of the lubricating oil) is preferably in the range of about 1.3:1 to about 6.0:1, or more preferably from about 1.4:1 to about 5.5:1, or more preferably from about 1.5:1 to about 5.2:1, or perhaps even more preferably from about 1.5:1 to about 4.8:1, or perhaps even more preferably from about 2.9:1 to about 4.7:1.

Suitable phenolic antioxidants useful in this disclosure include, for example, a substituted phenol that contains at least one alkyl substituent group. The phenolic antioxidant can include compounds free of nitrogen which are also ashless. The phenolic antioxidant can also include a substituted phenol containing at least two branched alkyl substituent groups. The phenolic antioxidant can further comprise a substituted phenol containing at least two branched alkyl substituent groups and an ester containing substituent group.

Illustrative phenolic antioxidants useful in this disclosure include, for example, a sterically hindered phenol that contains an alkyl group ortho to the hydroxyl group, two alkyl groups ortho to the hydroxyl group that occupy the 2-position and 6-position of the phenolic ring, or a mixture thereof. The alkyl groups can contain 1 to 24 carbon atoms, or 3 to 18 carbon atoms, or 3 to 12 carbon atoms. The alkyl groups can be linear, branched to include tertiary alkyl groups, or a mixture thereof. The sterically hindered phenol can also contain one or more additional alkyl groups and/or one or more hydrocarbyl groups such as a propionate ester group. Useful sterically hindered phenols can include ortho-alkylated phenolic compounds such as for example 2,6-ditertbutylphenol, 4-methyl-2,6-di-tertbutylphenol, 2,4,6-tritertbutylphenol, 2-tert-butylphenol, 2,6-diisopropylphenol, 2-methyl-6-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 4-(N,N-dimethylaminomethyl)-2,6-di-tertbutyl phenol, 4-ethyl-2,6-di-tertbutylphenol, and their analogs and homologs. Mixtures of two or more such mononuclear phenol compounds are also suitable.

Other illustrative phenolic antioxidants useful in this disclosure include, for example, an alkylene or alkylidene coupled sterically hindered phenol oligomer. The coupled sterically hindered phenol oligomer can contain two or more phenolic rings where each ring is occupied at the 2-, 4- and 6-positions by an alkyl group such as a methyl or t-butyl group or an arylalkyl group such as a 3,5-di-t-butyl-4-hydroxybenzyl group. The alkylene and alkylidene coupling groups can be respectively methylene and ethylidene groups. The alkyl groups can have 1 to 24 carbon atoms, 3 to 18 carbon atoms, or 3 to 12 carbon atoms. The alkyl groups can be linear, branched to include tertiary alkyl groups, or a mixture thereof. The coupled sterically hindered phenol oligomer can include a mixture of two or more oligomers where each oligomer contains a different number of phenolic rings. The coupling of the phenolic rings in an oligomer can be at ortho ring positions, at para ring positions, or at a mixture of ortho and para ring positions.

Still other illustrative phenolic antioxidants useful in this disclosure include a methylene coupled oligomer of a sterically hindered phenol such as for example 4,4′-methylene-bis(6-tert-butyl-2-methylphenol), 4,4′-methylene-bis(2-tert-amyl-6-methylphenol), 2,2′-methylene-bis(4-methyl-6-tert-butylphenol), 4,4′methylene-bis(2,6-di-tert-butylphenol), and similar compounds. In an embodiment of this disclosure, a methylene coupled oligomer of a sterically hindered phenol is 2,2′-methylene-bis(6-tert-butyl-4-dodecylphenol).

Illustrative phenolic antioxidants that may be used in combination with the aminic antioxidants include, for example, the following:

Suitable aminic antioxidants useful in this disclosure include, for example, monomeric amine antioxidants that are unsubstituted or hydrocarbon-substituted diphenyl amines, unsubstituted or hydrocarbyl-substituted phenyl naphthyl amines and unsubstituted or hydrocarbyl-substituted phenothiazines wherein the hydrocarbyl-substituted group is styrene or a C₁ to C₃₀ alkyl group, preferably a C₁ to C₁₀ alkyl group, more preferably a C₄ to C₁₀ alkyl group. Other monomeric aryl amines have been described in the patent literature.

Useful amine antioxidants include aromatic amine antioxidants. Other useful antioxidants include phenolic antioxidants (e.g., hindered phenolic antioxidants). Aromatic amine antioxidants are used in combination with phenolic antioxidants. Typical examples of amine antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_(X)R¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to 20 carbon atoms, and preferably contains from 6 to 12 carbon atoms. The aliphatic group can be a substituted aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic amine antioxidants have alkyl substituent groups of at least 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Particular examples of aromatic amine antioxidants useful in the present disclosure include: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine; phenyl-alpha-naphthylamine; and p-octylphenyl-alpha-naphthylamine.

Further, suitable aminic antioxidants useful in this disclosure include, for example, alkaryl amines and in some embodiments the aminic antioxidant is an alkylphenyl amine. Illustrative examples include a bis(4-alkylphenyl)amine.

The aminic antioxidant can include a secondary aromatic amine, typically a monoamine, that contains one aryl group, two aryl groups, or a mixture thereof. An illustrative aminic antioxidant is a secondary aromatic amine containing one aryl group such as for example N-methylaniline. The secondary aromatic amine containing one aryl group can also have C₁-C₁₆ alkyl or arylalkyl substituents on the aryl group. The secondary aromatic amine can also be a diarylamine such as for example diphenylamine, N-phenyl-1-naphthylamine, or combinations thereof. The diarylamine can contain one, two or more alkyl and/or arylalkyl substituents. The alkyl and arylalkyl substituents can have 1 to 16 carbon atoms, 3 to 14 carbon atoms, or 4 to 12 carbon atoms. The alkyl and arylalkyl substituents can be linear, branched, or a mixture thereof.

Illustrative aromatic aminic antioxidants that are used in combination with the phenolic antioxidants include, for example, the following:

Illustrative aminic and phenolic antioxidants useful in this disclosure are described, for example, in U.S. Patent Application Publication No. 2014/0296119, the disclosure of which is incorporated herein by reference.

The aminic antioxidants are used in combination the phenolic antioxidants. The aminic antioxidants may be used in an amount of 0.1 to 2.5 weight percent, preferably 0.1 to 2 weight percent, more preferably 0.1 to less than 1.5 weight percent.

The phenolic antioxidants may provide potential benefits in other performance aspects. The phenolic antioxidants may be used in an amount of 0.5 to 5 weight percent, preferably 0.05 to 4.5 weight percent, more preferably 0.5 to 4 weight percent. Preferably, the phenolic antioxidant component is present in the lubricating compositions at a minimum of 0.5, 0.6, 0.7, 1.0, 1.3, 2.0, 3.0, or a minimum 3.3 percent by weight or higher.

Other Additives

The formulated lubricating oil useful in the present disclosure may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to dispersants, detergents, antiwear additives, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, other antioxidants, seal compatibility agents, friction modifiers, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N.J. (1973); see also U.S. Pat. No. 7,704,930, the disclosure of which is incorporated herein in its entirety. These additives are commonly delivered with varying amounts of diluent oil, that may range from 5 weight percent to 50 weight percent.

Dispersants

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants used in the formulation of the lubricating oil may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the (poly)alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,2145,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458; 8,557,753. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from about 1:1 to about 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500 or more. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated dispersants, to form borated dispersants generally having from about 0.1 to about 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HNR₂ group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from about 500 to about 5000, or from about 1000 to about 3000, or about 1000 to about 2000, or a mixture of such hydrocarbylene groups, often with high terminal vinylic groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components.

Polymethacrylate or polyacrylate derivatives are another class of dispersants. These dispersants are typically prepared by reacting a nitrogen containing monomer and a methacrylic or acrylic acid esters containing 5-25 carbon atoms in the ester group. Representative examples are shown in U.S. Pat. Nos. 2,100,993, and 6,323,164. Polymethacrylate and polyacrylate dispersants are normally used as multifunctional viscosity modifiers. The lower molecular weight versions can be used as lubricant dispersants or fuel detergents.

Illustrative preferred dispersants useful in this disclosure include those derived from polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester, which dispersant has a polyalkenyl moiety with a number average molecular weight of at least 900 and from greater than 1.3 to 1.7, preferably from greater than 1.3 to 1.6, most preferably from greater than 1.3 to 1.5, functional groups (mono- or dicarboxylic acid producing moieties) per polyalkenyl moiety (a medium functionality dispersant). Functionality (F) can be determined according to the following formula:

F=(SAP×M _(n))/((112,200×A.I.)−(SAP×98))

wherein SAP is the saponification number (i.e., the number of milligrams of KOH consumed in the complete neutralization of the acid groups in one gram of the succinic-containing reaction product, as determined according to ASTM D94); M_(n) is the number average molecular weight of the starting olefin polymer; and A.I. is the percent active ingredient of the succinic-containing reaction product (the remainder being unreacted olefin polymer, succinic anhydride and diluent).

The polyalkenyl moiety of the dispersant may have a number average molecular weight of at least 900, suitably at least 1500, preferably between 1800 and 3000, such as between 2000 and 2800, more preferably from about 2100 to 2500, and most preferably from about 2200 to about 2400. The molecular weight of a dispersant is generally expressed in terms of the molecular weight of the polyalkenyl moiety. This is because the precise molecular weight range of the dispersant depends on numerous parameters including the type of polymer used to derive the dispersant, the number of functional groups, and the type of nucleophilic group employed.

Polymer molecular weight, specifically M_(n), can be determined by various known techniques. One convenient method is gel permeation chromatography (GPC), which additionally provides molecular weight distribution information (see W. W. Yau, J. J. Kirkland and D. D. Bly, “Modern Size Exclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979). Another useful method for determining molecular weight, particularly for lower molecular weight polymers, is vapor pressure osmometry (e.g., ASTM D3592).

The polyalkenyl moiety in a dispersant preferably has a narrow molecular weight distribution (MWD), also referred to as polydispersity, as determined by the ratio of weight average molecular weight (M_(w)) to number average molecular weight (M_(n)). Polymers having a M_(w)/M_(n) of less than 2.2, preferably less than 2.0, are most desirable. Suitable polymers have a polydispersity of from about 1.5 to 2.1, preferably from about 1.6 to about 1.8.

Suitable polyalkenes employed in the formation of the dispersants include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at least one C₃ to C₂ alpha-olefin having the formula H₂C═CHR¹ wherein R¹ is a straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and wherein the polymer contains carbon-to-carbon unsaturation, and a high degree of terminal ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of ethylene and at least one alpha-olefin of the above formula, wherein R¹ is alkyl of from 1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8 carbon atoms, and more preferably still of from 1 to 2 carbon atoms.

Another useful class of polymers is polymers prepared by cationic polymerization of monomers such as isobutene and styrene. Common polymers from this class include polyisobutenes obtained by polymerization of a C₄ refinery stream having a butene content of 35 to 75% by wt., and an isobutene content of 30 to 60% by wt. A preferred source of monomer for making poly-n-butenes is petroleum feed streams such as Raffinate II. These feed stocks are disclosed in the art such as in U.S. Pat. No. 4,952,739. A preferred embodiment utilizes polyisobutylene prepared from a pure isobutylene stream or a Raffinate I stream to prepare reactive isobutylene polymers with terminal vinylidene olefins. Polyisobutene polymers that may be employed are generally based on a polymer chain of from 1500 to 3000.

The dispersant(s) are preferably non-polymeric (e.g., mono- or bis-succinimides). Such dispersants can be prepared by conventional processes such as disclosed in U.S. Patent Application Publication No. 2008/0020950, the disclosure of which is incorporated herein by reference.

The dispersant(s) can be borated by conventional means, as generally disclosed in U.S. Pat. Nos. 3,087,936, 3,254,025 and 5,430,105.

Such dispersants may be used in an amount of about 0.01 to 20 weight percent or 0.01 to 10 weight percent, preferably about 0.5 to 8 weight percent, or more preferably 0.5 to 4 weight percent. Or such dispersants may be used in an amount of about 2 to 12 weight percent, preferably about 4 to 10 weight percent, or more preferably 6 to 9 weight percent. On an active ingredient basis, such additives may be used in an amount of about 0.06 to 14 weight percent, preferably about 0.3 to 6 weight percent. The hydrocarbon portion of the dispersant atoms can range from C₆₀ to C₁₀₀₀, or from C₇₀ to C₃₀₀, or from C₇₀ to C₂₀₀. These dispersants may contain both neutral and basic nitrogen, and mixtures of both. Dispersants can be end-capped by borates and/or cyclic carbonates. Nitrogen content in the finished oil can vary from about 200 ppm by weight to about 2000 ppm by weight, preferably from about 200 ppm by weight to about 1200 ppm by weight. Basic nitrogen can vary from about 100 ppm by weight to about 1000 ppm by weight, preferably from about 100 ppm by weight to about 600 ppm by weight.

Dispersants as described herein are beneficially useful with the compositions of this disclosure and substitute for some or all of the surfactants of this disclosure. Further, in one embodiment, preparation of the compositions of this disclosure using one or more dispersants is achieved by combining ingredients of this disclosure, plus optional base stocks and lubricant additives, in a mixture at a temperature above the melting point of such ingredients, particularly that of the one or more M-carboxylates (M=H, metal, two or more metals, mixtures thereof).

As used herein, the dispersant concentrations are given on an “as delivered” basis. Typically, the active dispersant is delivered with a process oil. The “as delivered” dispersant typically contains from about 20 weight percent to about 80 weight percent, or from about 40 weight percent to about 60 weight percent, of active dispersant in the “as delivered” dispersant product.

Detergents

Illustrative detergents useful in this disclosure include, for example, alkali metal detergents, alkaline earth metal detergents, or mixtures of one or more alkali metal detergents and one or more alkaline earth metal detergents. A typical detergent is an anionic material that contains a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically derived from an organic acid such as a sulfur-containing acid, carboxylic acid (e.g., salicylic acid), phosphorus-containing acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal. The detergent can be overbased as described herein.

The detergent is preferably a metal salt of an organic or inorganic acid, a metal salt of a phenol, or mixtures thereof. The metal is preferably selected from an alkali metal, an alkaline earth metal, and mixtures thereof. The organic or inorganic acid is selected from an aliphatic organic or inorganic acid, a cycloaliphatic organic or inorganic acid, an aromatic organic or inorganic acid, and mixtures thereof.

The metal is preferably selected from an alkali metal, an alkaline earth metal, and mixtures thereof. More preferably, the metal is selected from calcium (Ca), magnesium (Mg), and mixtures thereof.

The organic acid or inorganic acid is preferably selected from a sulfur-containing acid, a carboxylic acid, a phosphorus-containing acid, and mixtures thereof.

Preferably, the metal salt of an organic or inorganic acid or the metal salt of a phenol comprises calcium phenate, calcium sulfonate, calcium salicylate, magnesium phenate, magnesium sulfonate, magnesium salicylate, an overbased detergent, and mixtures thereof.

Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Useful detergents can be neutral, mildly overbased, or highly overbased. These detergents can be used in mixtures of neutral, overbased, highly overbased calcium salicylate, sulfonates, phenates and/or magnesium salicylate, sulfonates, phenates. The TBN ranges can vary from low, medium to high TBN products, including as low as 0 to as high as 600. Preferably the TBN delivered by the detergent is between 1 and 20. More preferably between 1 and 12. Mixtures of low, medium, high TBN can be used, along with mixtures of calcium and magnesium metal based detergents, and including sulfonates, phenates, salicylates, and carboxylates. A detergent mixture with a metal ratio of 1, in conjunction of a detergent with a metal ratio of 2, and as high as a detergent with a metal ratio of 5, can be used. Borated detergents can also be used.

Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀ or mixtures thereof. Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched and can be used from 0.5 to 6 weight percent. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.

In accordance with this disclosure, metal salts of carboxylic acids are preferred detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula

where R is an alkyl group having 1 to about 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, barium, or mixtures thereof. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.

Alkaline earth metal phosphates are also used as detergents and are known in the art.

Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See U.S. Pat. No. 6,034,039.

Preferred detergents include calcium sulfonates, magnesium sulfonates, calcium salicylates, magnesium salicylates, calcium phenates, magnesium phenates, and other related components (including borated detergents), and mixtures thereof. Preferred mixtures of detergents include magnesium sulfonate and calcium salicylate, magnesium sulfonate and calcium sulfonate, magnesium sulfonate and calcium phenate, calcium phenate and calcium salicylate, calcium phenate and calcium sulfonate, calcium phenate and magnesium salicylate, calcium phenate and magnesium phenate. Overbased detergents are also preferred.

The detergent concentration in the lubricating oils of this disclosure can range from about 0.5 to about 6.0 weight percent, preferably about 0.6 to 5.0 weight percent, and more preferably from about 0.8 weight percent to about 4.0 weight percent, based on the total weight of the lubricating oil.

As used herein, the detergent concentrations are given on an “as delivered” basis. Typically, the active detergent is delivered with a process oil. The “as delivered” detergent typically contains from about 20 weight percent to about 100 weight percent, or from about 40 weight percent to about 60 weight percent, of active detergent in the “as delivered” detergent product.

Viscosity Modifiers

Viscosity modifiers (also known as viscosity index improvers (VI improvers), and viscosity improvers) can be included in the lubricant compositions of this disclosure.

Viscosity modifiers provide lubricants with high and low temperature operability. These additives impart shear stability at elevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity modifiers include high molecular weight hydrocarbons, polyesters and viscosity modifier dispersants that function as both a viscosity modifier and a dispersant. Typical molecular weights of these polymers are between about 10,000 to 1,500,000, more typically about 20,000 to 1,200,000, and even more typically between about 50,000 and 1,000,000.

Examples of suitable viscosity modifiers are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity modifier. Another suitable viscosity modifier is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity modifiers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers are commercially available from Chevron Oronite Company LLC under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”); from Afton Chemical Corporation under the trade designation “HiTEC®” (such as “HiTEC® 5850B”; and from The Lubrizol Corporation under the trade designation “Lubrizol® 7067C”. Hydrogenated polyisoprene star polymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV200” and “SV600”. Hydrogenated diene-styrene block copolymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV 50”.

The polymethacrylate or polyacrylate polymers can be linear polymers which are available from Evnoik Industries under the trade designation “Viscoplex®” (e.g., Viscoplex 6-954) or star polymers which are available from Lubrizol Corporation under the trade designation Asteric™ (e.g., Lubrizol 87708 and Lubrizol 87725).

Illustrative vinyl aromatic-containing polymers useful in this disclosure may be derived predominantly from vinyl aromatic hydrocarbon monomer. Illustrative vinyl aromatic-containing copolymers useful in this disclosure may be represented by the following general formula:

A-B

wherein A is a polymeric block derived predominantly from vinyl aromatic hydrocarbon monomer, and B is a polymeric block derived predominantly from conjugated diene monomer.

In an embodiment of this disclosure, the viscosity modifiers may be used in an amount of less than about 10 weight percent, preferably less than about 7 weight percent, more preferably less than about 4 weight percent, and in certain instances, may be used at less than 2 weight percent, preferably less than about 1 weight percent, and more preferably less than about 0.5 weight percent, based on the total weight of the formulated oil or lubricating engine oil. Viscosity modifiers are typically added as concentrates, in large amounts of diluent oil.

As used herein, the viscosity modifier concentrations are given on an “as delivered” basis. Typically, the active polymer is delivered with a diluent oil. The “as delivered” viscosity modifier typically contains from 20 weight percent to 75 weight percent of an active polymer for polymethacrylate or polyacrylate polymers, or from 8 weight percent to 20 weight percent of an active polymer for olefin copolymers, hydrogenated polyisoprene star polymers, or hydrogenated diene-styrene block copolymers, in the “as delivered” polymer concentrate.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present disclosure if desired. These pour point depressant may be added to lubricating compositions of the present disclosure to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pour point depressants and/or the preparation thereof. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Seal Compatibility Agents

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride. Such additives may be used in an amount of about 0.01 to 3 weight percent, preferably about 0.01 to 2 weight percent.

Antifoam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 weight percent and often less than 0.1 weight percent.

Inhibitors and Antirust Additives

Antirust additives (or corrosion inhibitors) are additives that protect lubricated metal surfaces against chemical attack by water or other contaminants. A wide variety of these are commercially available.

One type of antirust additive is a polar compound that wets the metal surface preferentially, protecting it with a film of oil. Another type of antirust additive absorbs water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Yet another type of antirust additive chemically adheres to the metal to produce a non-reactive surface. Examples of suitable additives include zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure.

Illustrative friction modifiers may include, for example, organometallic compounds or materials, or mixtures thereof. Illustrative organometallic friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, molybdenum amine, molybdenum diamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates, and the like, and mixtures thereof. Similar tungsten based compounds may be preferable.

Other illustrative friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, alkoxylated fatty acid esters, alkanolamides, polyol fatty acid esters, borated glycerol fatty acid esters, fatty alcohol ethers, and mixtures thereof.

Illustrative alkoxylated fatty acid esters include, for example, polyoxyethylene stearate, fatty acid polyglycol ester, and the like. These can include polyoxypropylene stearate, polyoxybutylene stearate, polyoxyethylene isosterate, polyoxypropylene isostearate, polyoxyethylene palmitate, and the like.

Illustrative alkanolamides include, for example, lauric acid diethylalkanolamide, palmic acid diethylalkanolamide, and the like. These can include oleic acid diethyalkanolamide, stearic acid diethylalkanolamide, oleic acid diethylalkanolamide, polyethoxylated hydrocarbylamides, polypropoxylated hydrocarbylamides, and the like.

Illustrative polyol fatty acid esters include, for example, glycerol mono-oleate, saturated mono-, di-, and tri-glyceride esters, glycerol mono-stearate, and the like. These can include polyol esters, hydroxyl-containing polyol esters, and the like.

Illustrative borated glycerol fatty acid esters include, for example, borated glycerol mono-oleate, borated saturated mono-, di-, and tri-glyceride esters, borated glycerol mono-sterate, and the like. In addition to glycerol polyols, these can include trimethylolpropane, pentaerythritol, sorbitan, and the like. These esters can be polyol monocarboxylate esters, polyol dicarboxylate esters, and on occasion polyoltricarboxylate esters. Preferred can be the glycerol mono-oleates, glycerol dioleates, glycerol trioleates, glycerol monostearates, glycerol distearates, and glycerol tristearates and the corresponding glycerol monopalmitates, glycerol dipalmitates, and glycerol tripalmitates, and the respective isostearates, linoleates, and the like. On occasion the glycerol esters can be preferred as well as mixtures containing any of these. Ethoxylated, propoxylated, butoxylated fatty acid esters of polyols, especially using glycerol as underlying polyol can be preferred.

Illustrative fatty alcohol ethers include, for example, stearyl ether, myristyl ether, and the like. Alcohols, including those that have carbon numbers from C₃ to C₅₀, can be ethoxylated, propoxylated, or butoxylated to form the corresponding fatty alkyl ethers. The underlying alcohol portion can preferably be stearyl, myristyl, C₁₁-C₁₃ hydrocarbon, oleyl, isosteryl, and the like.

The lubricating oils of this disclosure exhibit desired properties, e.g., wear control, in the presence or absence of a friction modifier.

Useful concentrations of friction modifiers may range from 0.01 weight percent to 5 weight percent, or about 0.1 weight percent to about 2.5 weight percent, or about 0.1 weight percent to about 1.5 weight percent, or about 0.1 weight percent to about 1 weight percent. Concentrations of molybdenum-containing materials are often described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from 25 ppm to 700 ppm or more, and often with a preferred range of 50-200 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this disclosure. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

Antiwear Additives

A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) can be a useful component of the lubricating oils of this disclosure. ZDDP can be derived from primary alcohols, secondary alcohols or mixtures thereof. ZDDP compounds generally are of the formula

Zn[SP(S)(OR¹)(OR²)]₂

where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched. Alcohols used in the ZDDP can be propanol, 2-propanol, butanol, secondary butanol, pentanols, hexanols such as 4-methyl-2-pentanol, n-hexanol, n-octanol, 2-ethyl hexanol, alkylated phenols, and the like. Mixtures of secondary alcohols or of primary and secondary alcohol can be preferred. Alkyl aryl groups may also be used.

Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, The Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from for example Afton Chemical under the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from about 0.3 weight percent to about 1.5 weight percent, preferably from about 0.4 weight percent to about 1.2 weight percent, more preferably from about 0.5 weight percent to about 1.0 weight percent, and even more preferably from about 0.6 weight percent to about 0.8 weight percent, based on the total weight of the lubricating oil, although more or less can often be used advantageously. Preferably, the ZDDP is a secondary ZDDP and present in an amount of from about 0.6 to 1.0 weight percent of the total weight of the lubricating oil.

The types and quantities of performance additives used in combination with the instant disclosure in lubricant compositions are not limited by the examples shown herein as illustrations.

When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present disclosure are shown in Table 1 below.

It is noted that many of the additives are shipped from the additive manufacturer as a concentrate, containing one or more additives together, with a certain amount of base oil diluents. Accordingly, the weight amounts in the table below, as well as other amounts mentioned herein, are directed to the amount of active ingredient (that is the non-diluent portion of the ingredient). The weight percent (wt %) indicated below is based on the total weight of the lubricating oil composition.

TABLE 1 Typical Amounts of Other Lubricating Oil Components Approximate Approximate Compound wt % (Useful) wt % (Preferred) Antiwear 0.1-2  0.5-1 Dispersant 0.1-20 0.1-8 Detergent 0.1-20 0.1-8 Phenolic Antioxidant 0.1-10   2-5 Aminic Antioxidant 0.1-10 0.5-3 Friction Modifier 0.01-5   0.01-1.5 Pour Point Depressant 0.0-5   0.01-1.5 (PPD) Anti-foam Agent 0.001-3    0.001-0.15 Viscosity Index Improver 0.0-8  0.1-6 (pure polymer basis) Inhibitor and Antirust 0.01-5  0.01-1.5 

The foregoing additives are all commercially available materials. These additives may be added independently but are usually precombined in packages which can be obtained from suppliers of lubricant oil additives. Additive packages with a variety of ingredients, proportions and characteristics are available and selection of the appropriate package will take the requisite use of the ultimate composition into account.

The following non-limiting examples are provided to illustrate the disclosure.

EXAMPLES

Several engine oil formulations were prepared having the composition shown in FIGS. 1, 3 and 4. All of the ingredients used in the candidate formulated oils were commercially available.

The formulations shown in FIGS. 1, 3 and 4 are fully formulated lubricants. The formulations contain typical base stocks combined with dispersants, detergents, antiwear additives, friction modifiers, and the like.

FIG. 1 shows several inventive and comparative examples which were tested in the Volvo T-13 engine test (ASTM D8048) for oxidation performance. FIG. 2 shows the results of these tests. Officially, the two measurements of oxidation in the Volvo T-13 test are the 40° C. kinematic viscosity increase over the last 60 hours of the test (from 300-360 hours) (KV40) and the increase in oxidation peak height as measured by Fourier-transform infrared spectroscopy FT-IR (IR). Typical performance for engine oils containing antioxidants in oxidation tests such as the T-13 exhibits a “flat” region in which these measurements change very little over time, followed by a “breaking point” after which the KV40 and IR measurements increase rapidly. The breaking point typically corresponds to exhaustion of the antioxidant in the oil and can be used as a measurement of how well the antioxidants perform to protect the oil and hardware in the formulation. An increase in the “hours to break” indicates better performance.

FIG. 2 shows the performance of the inventive and comparative examples from FIG. 1 in the Volvo T-13 engine test.

FIG. 3 shows the performance of Comparative Examples 4 and 5 in the Sequence IITH (ASTM D8111) engine test, while FIG. 4 shows performance of additional comparative examples in the Mack T-12 (ASTM D7422) engine test. In FIG. 3, extended length Sequence IIIH tests were conducted, and the hours until 100 percent viscosity increase (based on KV40) was determined, a typical Sequence IIIH runs for 90 hours, while the tests shown in FIG. 3 were run for up to 180 hours, or until 150% KV40 increase was observed.

FIG. 4 shows performance of inventive and comparative examples in the Mack T-12 engine test (ASTM D7422). The used oil lead parameters measured in this test represent one measure of the oxidation performance of these examples, as lead from the engine bearings is produced due to corrosion by acidic byproducts of lubricant oxidation (with higher values of lead corresponding to a higher level of lubricant oxidation). Comparing these used oil lead values with those presented in FIG. 2 for the Volvo T-13 engine test demonstrates surprising performance features of the disclosed inventive compositions.

As measured in the Volvo T-13, inventive examples show end of test used oil lead increases of less than 100 ppm, or more preferably less than 90 ppm, or more preferably less than 80 ppm, or more preferably less than 70 ppm, or more preferably less than 60 ppm, or more preferably less than 50 ppm, or more preferably less than 40 ppm, or more preferably less than 30 ppm, or more preferably less than 20 ppm, or more preferably less than 10 ppm.

As measured in the Volvo T-13, inventive examples show KV40 Time to Break values of about 252 hours or more, or more preferably about 260 hours or more, or more preferably about 270 hours or more, or more preferably about 276 hours or more, or more preferably about 280 hours or more, or even more preferably about 288 hours or more. In some examples, inventive compositions may have a KV40 Time to break of 292 hours or more, or even 300 hours or more.

As measured in the Volvo T-13, inventive examples show an FTIR oxidation peak height at end of test of about 175 Abs/cm or less, or more preferably about 150 Abs/cm or less, or more preferably about 125 Abs/cm or less. In some examples, inventive compositions may have an FTIR oxidation peak height at end of test of about 100 Abs/cm or less, or more preferably about 75 Abs/cm or less, or even more preferably about 50 Abs/cm or less, or even more preferably of about 40 Abs/cm or less.

As measured in the Volvo T-13, inventive examples show a relative KV40 increase from 300-360 hours of about 100% or less, or more preferably about 90% or less, or more preferably about 80% or less. In some examples, inventive compositions may have relative KV40 increase from 300-360 hours may be about 70% or less, or more preferably about 60% or less, or more preferably about 50% or less, or more preferably about 40% or less, or even more preferably about 30% or less, or even more preferably about 25% or less, or even more preferably about 10% or less.

It has been surprisingly found that formulations comprising a combination of lubricating oil base stocks, an aminic antioxidant, and a hindered phenolic antioxidant, show significantly improved oxidation protection performance in the Volvo T-13 engine test. Surprisingly, when the ratio of the hindered phenolic antioxidant to the aminic antioxidant is greater than about 1.5:1 (based on the weight percent of each component compared to the total weight of the lubricating oil) the time to break (both for the KV40 and the IR oxidation peak height) is significantly increased as compared to lubricating oil compositions comprising a combination of lubricating oil base stocks and an aminic antioxidant and phenolic antioxidant with a ratio of phenolic to aminic antioxidant that is less than about 1.5:1.

This is observed when comparing Comparative Examples 1 and 2 with Examples 1 through 4. Comparative Examples 1 and 2 show a time to break which is less than about 288 hours, and both of these formulations fail the Volvo T-13 test when comparing performance against the limits set forth for the API CK-4 and FA-4 performance categories (as listed in ASTM D4485). In FIG. 2, Examples 1 through 4 have increasingly higher levels of hindered phenolic antioxidant while the level of aminic antioxidant remains fixed. Surprisingly, the time to break in the Volvo T-13 continues to increase as the level of hindered phenolic antioxidant increases (and also as the level of the ratio of concentration the hindered phenolic antioxidant to the aminic antioxidant increases).

It has additionally been surprisingly found that using a lubricant composition comprising a lubricating oil base stock, wherein the lubricating oil base stock comprises at least one Group V base stock in an amount from about 1 to about 20 weight percent (based on the total weight of the lubricating oil), at least one hindered phenolic antioxidant and at least one aminic antioxidant, such that the ratio of hindered phenolic antioxidant to the aminic antioxidant is about 1.5:1 to about 6.0:1 (based on the weight percent of each component as compared to the total weight of the lubricating oil) shows improved oxidation performance as measured in the Volvo T-13 engine test.

This is demonstrated in FIG. 2 when comparing Comparative Example 3 and Example 1. Comparative Example 3 contains no Group V base stock but has a hindered phenol antioxidant to aminic antioxidant ratio of about 2.8:1. This example showed a time to break in the Volvo T-13 of about 252 hours, while Example 1 (which contains 9 weight percent Group V base stock, specifically alkylated naphthalene) shows a significantly increased time to break in the Volvo T-13 of about 300 hours. In fact, Comparative Example 3 exhibited such a dramatic increase in oxidation in the Volvo T-13, as evidenced by the rapid increase end of test delta Pb, the test had to be terminated at approximately 288 hours to prevent catastrophic engine damage.

The improved performance of Examples 1 through 4 in FIG. 2 is surprising. It is generally accepted that hindered phenolic antioxidants offer improved performance at lower temperatures, while aminic antioxidants offer improved oxidation performance at higher temperatures. This behavior is observed in a number of bench and engine oxidation tests. For example, FIG. 3 shows the performance Comparative Examples 4 and 5 in the Sequence IIIH (ASTM D8111) engine test. The Sequence IIIH is a new oxidation engine test developed for the ILSAC GF-6 category for passenger car motor oils. The Sequence IIIH measures lubricant oxidation performance by examining the deposit forming tendencies and ability of the lubricant to control oxidatively induced viscosity increase.

As shown in FIG. 3, Comparative Example 5 has more than twice the concentration of hindered phenolic antioxidant as compared to Comparative Example 4. Here the viscosity increase for Comparative Example 5 is higher, and the time to 100 percent viscosity increase shorter as compared to Comparative Example 4. Comparative Example 4 has a hindered phenolic antioxidant to aminic antioxidant ratio of about 1.8:1 (based on the weight percent of each component as compared to the weight of the entire lubricant composition), while Comparative Example 5 has a hindered phenolic antioxidant to aminic antioxidant ratio of about 3.8:1. These ratios are within the preferred ranges as discussed previously, but do not show the surprising and unexpected improved performance which was observed in the Volvo T-13 engine test.

These results demonstrate the unique and unanticipated performance attributes of the lubricant compositions of this disclosure for improving lubricant oxidation performance for engines operating at high temperatures and/or for long service intervals. The table below shows a comparison of the oil gallery temperatures for the Volvo T-13, Mack T-12, and Sequence IIIH. This table further shows the lubricating compositions of this disclosure demonstrate surprising and unexpected performance benefits.

Oil Gallery Temperatures for Selected Engine Oxidation Tests Volvo T-13 130° C. Mack T-12 Phase 1 88° C./Phase 2 116° C. Sequence IIIH 150° C.

FIG. 4 further demonstrates the surprising and unexpected performance benefits of the lubricant compositions of this disclosure. FIG. 4 shows results of the Mack T-12 engine test for Example 5 and Comparative Example 1. The Mack T-12 engine test is generally accepted as the predecessor test to the Volvo T-13. The Mack T-12 measures lubricant oxidation by examining the concentration of Lead (Pb) in the used oil at the end of test and during the last 50 hours of the test. Pb is generated from the bearings in the Mack T-12 as the lubricant oxidizes and produces organic acids as by-products of said oxidation. Samples which produce higher levels of Pb in the used oil are considered to have poorer oxidation performance.

Example 5 surprisingly shows 22 ppm of Pb at the end of test while Comparative Example 1 shows half of that (11 ppm). Furthermore, during the last 50 hours of the test, the increase in Pb concentration is nearly 3-times higher for Example 5 as compared to Comparative Example 1. This significantly higher increase in Pb is indicative that the oil is more rapidly generating organic acids from lubricant oxidation as compared to the lubricant composition of Comparative Example 1. These results further demonstrate the surprising and unexpected performance of the lubricant compositions of this disclosure, as these results show these lubricant compositions provide improved performance as measured in the Volvo T-13 which is contrary to the general understanding of the performance benefits provided by lubricant compositions comprising one more hindered phenolic antioxidants, one or more aminic antioxidants, and from about 1 weight percent to about 20 weight percent (based on the total weight of the lubricating oil composition) of Group V base stock. It is important to note that while the inventive compositions, surprisingly, do not show improved oxidation performance in the Mack T-12 engine tests, the inventive compositions are still capable of passing the test against the API CK-4 and API FA-4 limits as outlined in ASTM D4485.

PCT and EP Clauses:

1. A method for improving oxidative stability of a lubricating oil in a diesel engine by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component; and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components; wherein the lubricating oil base stock is present in an amount from 1 to 95 weight percent, based on the total weight of the lubricating oil; wherein the at least one aminic antioxidant is present in an amount from 0.1 to 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from 0.5 to 5 weight percent, and the at least one Group V base stock is present in an amount from 1 to 20 weight percent, all based on the total weight of the lubricating oil; and wherein oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048.

2. The method of clause 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the number of hours to break as measured by Fourier-transform infrared spectroscopy (FT-IR) or by kinematic viscosity at 40° C. (KV40) of said lubricating oil, is greater than 252 hours as compared to the number of hours to break as measured by FT-IR or KV40 of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.

3. The method of clause 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of said lubricating oil, is less than 100 percent increase as compared to the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.

4. The method of clause 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the amount of lead present in end of test used oil of said lubricating oil, is less than 100 ppm as compared to the amount of lead present in end of test used oil of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.

5. The method of clause 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the FTIR oxidation peak height at end of test, is less than 175 Abs/cm as compared to the FTIR oxidation peak height at end of test of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.

6. The method of clauses 1-5 wherein the at least one phenolic antioxidant comprises a substituted phenol that contains at least one alkyl substituent group; a sterically hindered phenol that contains an alkyl group ortho to the hydroxyl group, or two alkyl groups ortho to the hydroxyl group that occupy the 2-position and 6-position of the phenolic ring, or a mixture thereof; or an alkylene or alkylidene coupled sterically hindered phenol oligomer.

7. The method of clauses 1-6 wherein the at least one phenolic antioxidant comprises a substituted phenol containing at least one alkyl substituent group.

8. The method of clauses 1-7 wherein the at least one phenolic antioxidant comprises

9. The method of clauses 1-8 wherein the at least one aminic antioxidant comprises an alkylated diphenylamine, phenyl naphthylamine, phenothiazine, imidodibenzyl, or diphenyl phenylene diamine.

10. The method of clauses 1-9 wherein the at least one aminic antioxidant comprises an alkylated diarylamine.

11. The method of clauses 1-10 wherein the at least one aminic antioxidant comprises an alkylated diarylamine.

12. The method of clauses 1-11 wherein the at least one aminic antioxidant comprises

13. The method of clauses 1-12 wherein the ratio of the concentration of at least one phenolic antioxidant to the at least one aminic antioxidant is from 1.5:1 to 6.0:1 based on the total weight of the lubricant composition.

14. The method of clauses 1-13 wherein the at least one Group V base stock is an alkylated naphthalene.

15. A lubricating oil having a composition comprising a lubricating oil base stock as a major component; and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components; wherein the lubricating oil base stock is present in an amount from 1 to 95 weight percent, based on the total weight of the lubricating oil; wherein the at least one aminic antioxidant is present in an amount from 0.1 to 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from 0.5 to 5 weight percent, and the at least one Group V base stock is present in an amount from 1 to 20 weight percent, all based on the total weight of the lubricating oil; and wherein oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. 

1. A method for improving oxidative stability of a lubricating oil in a diesel engine by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component; and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components; wherein the lubricating oil base stock is present in an amount from about 1 to about 95 weight percent, based on the total weight of the lubricating oil; wherein the at least one aminic antioxidant is present in an amount from about 0.1 to about 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from about 0.5 to about 5 weight percent, and the at least one Group V base stock is present in an amount from about 1 to about 20 weight percent, all based on the total weight of the lubricating oil; and wherein oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048.
 2. The method of claim 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the number of hours to break as measured by Fourier-transform infrared spectroscopy (FT-IR) or by kinematic viscosity at 40° C. (KV40) of said lubricating oil, is greater than about 252 hours as compared to the number of hours to break as measured by FT-IR or KV40 of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 3. The method of claim 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of said lubricating oil, is less than about 100 percent increase as compared to the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 4. The method of claim 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the amount of lead present in end of test used oil of said lubricating oil, is less than about 100 ppm as compared to the amount of lead present in end of test used oil of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 5. The method of claim 1 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the FTIR oxidation peak height at end of test, is less than about 175 Abs/cm as compared to the FTIR oxidation peak height at end of test of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 6. The method of claim 1 wherein the at least one phenolic antioxidant comprises a substituted phenol that contains at least one alkyl substituent group; a sterically hindered phenol that contains an alkyl group ortho to the hydroxyl group, or two alkyl groups ortho to the hydroxyl group that occupy the 2-position and 6-position of the phenolic ring, or a mixture thereof; or an alkylene or alkylidene coupled sterically hindered phenol oligomer.
 7. The method of claim 1 wherein the at least one phenolic antioxidant comprises a substituted phenol containing at least one alkyl substituent group.
 8. The method of claim 1 wherein the at least one phenolic antioxidant comprises


9. The method of claim 1 wherein the at least one aminic antioxidant comprises an alkylated diphenylamine, phenyl naphthylamine, phenothiazine, imidodibenzyl, or diphenyl phenylene diamine.
 10. The method of claim 1 wherein the at least one aminic antioxidant comprises an alkylated diarylamine.
 11. The method of claim 1 wherein the at least one aminic antioxidant comprises


12. The method of claim 1 wherein the at least one aminic antioxidant is present in an amount from about 0.5 to about 2 weight percent, and the at least one phenolic antioxidant is present in an amount from about 0.5 to about 4.5 weight percent, based on the total weight of the lubricating oil.
 13. The method of claim 1 wherein the ratio of the concentration of at least one phenolic antioxidant to the at least one aminic antioxidant is from about 1.5:1 to about 6.0:1 based on the total weight of the lubricant composition.
 14. The method of claim 1 wherein the lubricating oil base stock comprises a Group I, Group II, Group III, Group IV or Group V base oil.
 15. The method of claim 1 wherein the at least one Group V base stock is an alkylated naphthalene.
 16. The method of claim 1 wherein the lubricating oil base stock is present in an amount from about 5 to about 90 weight percent, based on the total weight of the lubricating oil.
 17. The method of claim 1 wherein the formulated oil further comprises one or more of a viscosity modifier, dispersant, detergent, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive.
 18. The method of claim 1 wherein the lubricating oil is a passenger vehicle engine oil (PVEO) or a commercial vehicle engine oil (CVEO).
 19. A lubricating oil having a composition comprising a lubricating oil base stock as a major component; and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components; wherein the lubricating oil base stock is present in an amount from about 1 to about 95 weight percent, based on the total weight of the lubricating oil; wherein the at least one aminic antioxidant is present in an amount from about 0.1 to about 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from about 0.5 to about 5 weight percent, and the at least one Group V base stock is present in an amount from about 1 to about 20 weight percent, all based on the total weight of the lubricating oil; and wherein oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048.
 20. The lubricating oil of claim 19 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the number of hours to break as measured by Fourier-transform infrared spectroscopy (FT-IR) or by kinematic viscosity at 40° C. (KV40) of said lubricating oil, is greater than about 252 hours as compared to the number of hours to break as measured by FT-IR or KV40 of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 21. The lubricating oil of claim 19 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of said lubricating oil, is less than about 100 percent increase as compared to the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 22. The lubricating oil of claim 19 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the amount of lead present in end of test used oil of said lubricating oil, is less than about 100 ppm as compared to the amount of lead present in end of test used oil of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 23. The lubricating oil of claim 19 wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the FTIR oxidation peak height at end of test, is less than about 175 Abs/cm as compared to the FTIR oxidation peak height at end of test of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock.
 24. The lubricating oil of claim 19 wherein the at least one phenolic antioxidant comprises a substituted phenol that contains at least one alkyl substituent group; a sterically hindered phenol that contains an alkyl group ortho to the hydroxyl group, or two alkyl groups ortho to the hydroxyl group that occupy the 2-position and 6-position of the phenolic ring, or a mixture thereof; or an alkylene or alkylidene coupled sterically hindered phenol oligomer.
 25. The lubricating oil of claim 19 wherein the at least one phenolic antioxidant comprises a substituted phenol containing at least one alkyl substituent group.
 26. The lubricating oil of claim 19 wherein the at least one phenolic antioxidant comprises


27. The lubricating oil of claim 19 wherein the at least one aminic antioxidant comprises an alkylated diphenylamine, phenyl naphthylamine, phenothiazine, imidodibenzyl, or diphenyl phenylene diamine.
 28. The lubricating oil of claim 19 wherein the at least one aminic antioxidant comprises an alkylated diarylamine.
 29. The lubricating oil of claim 19 wherein the at least one aminic antioxidant comprises


30. The lubricating oil of claim 19 wherein the at least one aminic antioxidant is present in an amount from about 0.5 to about 2 weight percent, and the at least one phenolic antioxidant is present in an amount from about 0.5 to about 4.5 weight percent, based on the total weight of the lubricating oil.
 31. The lubricating oil of claim 19 wherein the ratio of the concentration of at least one phenolic antioxidant to the at least one aminic antioxidant is from about 1.5:1 to about 6.0:1 based on the total weight of the lubricant composition.
 32. The lubricating oil of claim 19 wherein the lubricating oil base stock comprises a Group I, Group II, Group III, Group IV or Group V base oil.
 33. The lubricating oil of claim 19 where in the at least one Group V base stock is an alkylated naphthalene.
 34. The lubricating oil of claim 19 wherein the lubricating oil base stock is present in an amount from about 5 to about 90 weight percent, based on the total weight of the lubricating oil.
 35. The lubricating oil of claim 19 which further comprises one or more of a viscosity modifier, dispersant, detergent, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive.
 36. The lubricating oil of claim 19 which is a passenger vehicle engine oil (PVEO) or a commercial vehicle engine oil (CVEO). 